1. Field of the Invention
The present invention relates to an air bleed device for an automotive vehicle enclosed housing, such as an axle housing or a gear housing.
2. Description of Prior Art
Generally, in the case of a power transmission device and the like of a vehicle, the meshing engagement of the gears generates heat within a housing of the device which raises the air temperature therein when the vehicle is in operation. When the vehicle is not in operation, the heat is dissipated to decrease the air temperature. This variation in temperature causes a pressure difference between air outside and inside of the housing. To prevent this, it is common to mount an air bleed device to said housing to provide communication between the inside and outside of the housing. Conventional air bleed devices of this kind are illustrated in FIGS. 7 and 8.
FIG. 7 shows a first conventional air bleed device A mounted to an axle housing 1 of the banjo type. According to this air bleed device A, a bolt 2, threadedly engaged with the housing 1, is formed with a connecting passage 3, and at the upper portion of said connecting passage 3, the bolt 2 is formed with a vent hole 4 communicating with the connecting passage 3, and a cap 5, formed at its peripheral edge portion with a cutout 5a, is mounted to cover said bolt 2 to prevent the entry of rain drops and dust into the connecting passage 3. On the inner side of the housing 1, a baffle 6 to cover said bolt 2 is welded in a manner to open on one side so as to prevent the lubricant oil flushed due to the centrifugal force of a rotating ring gear of a final gearing or of a differential device from flowing outwardly of the housing 1 through the connecting passage 3.
FIG. 8 shows a second conventional air bleed device A according to which a baffle 6 having a flange 6a is welded to a casing. A bolt having a connecting passage 3 drilled therethrough is threadedly engaged in said baffle 6, and a plate 16 is placed on the top upper surface of the bolt 2 and then covered by a cap 5 and with a spring 17 within said cap 5. The plate 16 is biased toward the head of the bolt 2 to close the connecting passage 3. With this construction, when the inner pressure of the housing 1 increases above a predetermined pressure, the plate 16 is urged against the predetermined resilient force of the spring 17 to open the connecting passage 3, and with this construction the entry of rain drops and dust is prevented.
However, these conventional air bleed devices A, require a large-number of component parts including baffle 6, bolt 2, cap 5, plate 16, spring and the like. In addition, since the baffle 6 is welded to the housing 1 and the bolt 2 is threadedly engaged with the housing 1 or baffle 6, the workability upon mounting the air bleed device A to the housing 1 is poor, thus inviting an increase in weight and cost.